Commissioning a linear accelerator (LINAC) for clinical use typically requires a water tank dosimetry scanner. By way of example, for commissioning a treatment planning system (TPS) for clinical use, medical physicists are faced with a need for precision during set up of measuring equipment and testing. Since commissioning beam data is treated as a reference and ultimately used by the TPS, it is vitally important that collected (i.e., scanned) data be of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor treatment outcome. It is therefore important that the scanner being used, regardless of style, must be stable under typical use conditions. In particular, and by way of example, a table used to support the scanner should be able to support the weight of a tank filled with water while maintaining stability. There needs to be stability while personnel work around the table supporting the scanner, especially when there are portions of the floor that are typically unstable, such as the bearing floor portion used to rotate the couch. The table should be able to maintain its stability during weight load changes as water is added and removed from the tank during, by way of example, tissue phantom ratio (TPR) measurements.
In addition to stability during measurement procedures, there remains a need for stability and portability during transport of the tank at a facility and storage at that or related facility. Also, there remains a need for stability and portability such that the scanner will not be damaged or unacceptably misaligned during transport between facilities.
As described in U.S. Pat. No. 8,321,179 for Multiple Axes Scanning System and Method for Measuring Radiation from a Radiation Source, the contents of which are hereby incorporated by reference in their entirety, there is a need for an accurate scan measurement of relative dose in a water phantom.
The measurement session of the LINAC beam scanning can take many days. During these long scanning times, there are no assurances from the radiation measurement scanning system to indicate that the scanning system or the LINAC has not changed during scans in a way that would affect the measurement data. It is incumbent upon the operator to perform periodic quality assurance (QA) tests that would reveal such changes in the scanner system. The measurement session of the LINAC beam scanning will typically include many setups. During these many setups, it is important to know that the measuring equipment has been properly and reproducibly installed. The stability or lack thereof provided by the table is clearly important.
The use of a LINAC for external beam irradiation and radiotherapy is well known. As presented in U.S. Pat. No. 5,160,337 to Cosman (the contents of which are also herein incorporated by reference in their entirety), a LINAC delivers a beam of photons or electrons through a collimated slit system and has multiple degrees of freedom, wherein a gantry rotates about a horizontal axis that is defined by a gantry bearing anchored to a housing which is anchored to the floor. The gantry can swing in an arc. The photon beam emerges from a collimator and aims at a target. A couch is connected to a rotating floor bearing, and both the floor bearing and the couch rotate about a vertical axis. In use, a patient lies on top of the movable couch, which can move in multiple directions to locate an anatomical target at the intersection of two axes, referred to as the isocenter of the LINAC. The couch sweeps around the vertical axis along an arc in a horizontal plane.
The couch is attached via the floor bearing and rotates about the vertical axis. In the event that the floor or couch bearing is unstable, stability can be achieved by an independent, collision-free or curved-shaped floor stand by anchoring a bearing mount to the floor. The fact that the bearing is independent of the couch bearing can result in aberrations in the stability of the floor bearing relative to the vertical axis.
There is a need for a support for radiation measuring systems that can accommodate various LINAC setups and be sufficiently portable to allow a user to efficiently and effectively move radiation measuring equipment into place with an assurance of accuracy and repeatability.